Field
Embodiments of the invention relate to designs of, and methods of manufacturing, a waveguide structure with a patterned contact wire.
Background
Integrated optical circuits (IOC), analogous to integrated electronic circuits, comprise optical components formed on a substrate. A commonly used optical component is an integrated waveguide. The waveguides are used to guide light between various other components on the chip. The waveguides may be either strip or rib type and are formed by etching trenches in a structural layer of light guiding material. The trenches create a step difference in the refractive index, which provides light confinement and assures light propagation within the waveguide. Depending on the application, the waveguides may be of different thicknesses and the rib or strip height might be on the order of several microns thick. The application of integrated optics is most common in fiber optic communication, though many other applications exist. Common optical functions for which integrated optics are utilized include directional switching, phase modulation and intensity modulation.
Waveguides are typically covered by a cladding layer which, in the case of silicon waveguides, may be thermally grown silicon dioxide. Many active integrated optical systems have been based on silicon. The advantages of silicon integrated optical devices include the potential use of standard silicon integrated electronic circuit manufacturing technology and the integration of optical and electronic circuits on one silicon device. For the effective use of silicon integrated optics, it is considered important to produce both a low-loss waveguide structure and an electrically controllable modulating element. For this purpose, waveguides and electrical contact wires are fabricated on the same chip. The layout may require the waveguides and wires to cross each other in order to effectively use the room on chip, or to contact any active elements located on top of the waveguide.